Thanks a lot to LaszloNagy and Marc H for the support and for answering my questions!
For LaszloNagy: looking at how the 3d body is generated, I was able to verify the correctness of the measurements and values I sought! I don't think the differences in values between the layers of the two composite walls, in my case, depended on the priority number of the intersection of their building materials because the two composite walls were made with the same materials and therefore had the same properties as intersection....
For Marc H: ... actually I have experienced that, between the two composite walls, the one with the layers of greatest surface and volume turns out to be the wall traced first, regardless of the direction of tracing !!! ...and yes! the diagonal cut would be unrealistic so I'm glad Archicad reasons as it does.
The really strange thing is the impossibility of pulling out the length and height of the various layers, because I think these data are already kept inside the drawing and it would be right for the programmers to bring them to light!
Thanks again, I hope I won't have to disturb you again, but I fear it will happen!